Full waveform sonic data, acquired in a borehole penetrating a North Sea reservoir, were used to explore new techniques for analysis and interpretation of sonic data. Analysis of direct sonic arrivals included correlations with core-derived permeability, inversion for compressional and shear velocities, and interpretation of compressional and shear velocities in terms of formation parameters. The velocities are found to be sensitive indicators of lithology and water saturation. In addition to the standard processing for compressional and shear velocities, inversion of sonic traveltimes resulted in a compressional wave-velocity log with a 0.15 m vertical resolution. Using a process similar to prestack seismic migration, reflected sonic arrivals were used to form images of bedding features to a distance of 12 m from the borehole. The well intersects a region of strong normal faulting. Locations of high angle features and strong dip changes on the sonic-derived images were consistent with the locations of faults indicated on the dipmeter-derived structural cross-sections.

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